The Vulnerability Spiral: Compound Climate Risk Across Five Islands

SAKSHI D. MASKE 

Small islands are widely assumed to face a compounding climate risk: high physical exposure to sea-level rise, layered on top of degrading natural coastal defenses. That assumption is rarely tested against independent, multi-temporal evidence, and rarely broken down by ecosystem type — so I tested it directly, across five islands spanning three ocean basins: Maldives, Lakshadweep, Seychelles, Fiji, and the Canary Islands. I treated mangrove and coral reef degradation as two independent pathways rather than one undifferentiated category. Physical exposure came from settlement-level elevation data; mangrove extent I tracked across three independent time points (1996, 2010, 2020); coral condition came from a 24-year, monthly-sampled satellite-derived thermal-stress record (1996–2020). Coral reef systems show a measurable, rising bleaching-stress trend in four of five islands, most severely in Seychelles. Mangroves, tested with the same rigor, show no measurable decline in any of the three islands where they're present — this doesn't support the assumption that ecosystem decline is uniform. Combine physical exposure with coral degradation into a composite vulnerability score, and the island with the highest physical exposure (Maldives) is not the island with the highest overall compound risk (Seychelles) — exposure alone is an incomplete vulnerability measure. I also ran a supplementary test of whether formal protected-area coverage aligns with this empirically verified risk, and found a positive but not statistically significant relationship, consistent with a small-sample limitation rather than a genuine absence of governance responsiveness. A descriptive comparison of settlement expansion (2016–2024) adds a third, corroborating signal: Seychelles shows the clearest sign of building pressure on its ecosystem buffers, while Fiji shows none. Coastal ecosystem degradation, in other words, isn't a uniform phenomenon across ecosystem types — with direct implications for how adaptation and conservation resources get prioritized.